Magic Medicine

Those are some incredible numbers!

Congrats

Sean H

ttt

cobra marty

I see that with the smaller pulley you make 22psi at 6800rpm and great peak HP and 1400TQ but how was the bigger pulley with 22psi at a more reasonable 6200rpm? Sure you will lose some peak HP bragging numbers but I would bet that the TQ curve will be higher. Do you have a curve with the larger pulley?

cobra marty

What I am saying is with the larger pulley and a rpm limit of 6200rpm you still have a max boost of 22psi but you will bump up the boost curve by about 25% across the whole boost curve and that will bump up the TQ curve by about the same 25% and would see 1500TQ (13psi instead of 10psi) at 4850rpm and 1750TQ (22psi instead of 18psi) at 6200rpm which is WOW! 2066HP at 6200rpm! I just don't think that you need to spin the motor to that crazy 6800rpm to get the power.

cobra marty

And the PSI blower making 1500-1550 HP, What is it's Torque?

tomcat

Hi Marty:

Since air flow only goes up as ~ square root (P2/P1) your numbers are a too optimistic.

With the big crank pulley we saw an additional ~100 ft-lbs @ 6200. To get to 2000 HP you would have to be able to carry that 1500 ft-lbs out to 7000 RPM. This is a tempting prospect, but I would rather see a reliable package around the 1800 HP level first.

In any case, it makes more sense to keep the smaller crank pulley and spin the engine as fast as possible. Although it's a challenge for the engine builder, more RPM is an advantage in racing because it gives a higher top speed for a given prop. Especially in record runs where some boats may be running out of pitch and gear options.

I have not made a comparison between the curves of the two different blower systems. The PSI will certainly have more power down low and it will be interesting to see where the crossover occurs. I am told that racing rarely dips below 4500 RPM so that would be a good target as you were deciding about cams and other things that affect the torque curve. This would be part of the process of developing a centrifugal "package".

I'm glad I'm not an engine builder. Just when you get an engine package worked out, everybody wants more power.

cobra marty

You're right, it depends on the application. For a speed run you have it down right- carry torque as far up in the rpm. Nice stuff.

44MTI

I believe that motor with the PSI, has made over 1700 hp, with 18# of boost. I also believe the quad whipple made just north of 1600. Both of these have been slightly detuned for the sake of reliablity.

tomcat

Hi 42MTI:

I'm sure that Sterling could make 1800 HP with a PSI on that engine if they wanted to, but they send them out the door to customers at 1530 HP. Why not send them out at 1600, 1700 or 1800 HP? I think there's two or three possible reasons.

1) manifold air temps too high/detonation risk
2) parasitic blower drive losses/belt and blower drive problems
3) cylinder pressures too high for engine components

We've taken a big step forward with an intercooler that is almost 3X as large as the core under the PSI blower. We have evidence that drive losses are lower with the centrifugal blowers, which should reduce belt and blower drive problems. Reducing parasitic loss is also important for number 3, since it reduces the gross HP that the engine is required to produce before "paying for the blower".

Improvements in these areas should allow professional engine builders to increase the HP level that they would be willing to send out the door to customers. That's the best definition of reliablity I can think of in this arena.

Tom

GPM

Dyno sheets on Whipple motors are harder to find than cheap gas. The only one I've ever seen was from Paul Pfaff, one of his Quadrotor 598s, it made 1273 hp @ 6700 with 18 lb of boost. The motor had standard cnc Pro 1 heads.